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New approaches to monitoring of cardiac function
KTH, School of Technology and Health (STH).
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Left ventricular pumping performance may be described by intraventricular pressure and volume variables, usually presented as a pressure-volume plot. However, on-line monitoring of left ventricular pressure and volume with high temporal resolution requires the use of an invasive catheter technique such as, for example, the conductance catheter method. On the other hand, the very invasiveness and complexity of this approach makes it less suitable for clinical use. It is then not surprising that there has been long-felt need to make the conductance method less invasive and attempts have been made to adjust the method to clinical demands and routine in order to extract more information from pressure-volume interplay and possibly translate relevant data to their non-invasive estimates.

In the present studies, a standard five segmental conductance catheter was used in animal (pig) experiments. Segmental conductances were compared to global conductance. Since the mid-ventricular segment was shown to reflect global volume, which was also shown on theoretical basis, it was concluded that a single segmental catheter most probably could be used to estimate global left ventricular volume.

Subsequently, a thin and flexible single segmental conductance catheter was constructed and applied to an animal (pig) experimental model. Results were reproducible and very few arrythmias were detected.

At the next stage, left ventricular isovolumic phases were investigated using the standard conductance catheter method, as well as echocardiographically derived tissue velocity doppler. Conductance was shown to decrease during isovolumic contraction, and an adjustment method was proposed in order to account for the subsequent decrease in pressure-volume loop area.

In separate experiments, the left ventricular pressure wave form during left ventricular systole was examined, and an algorithm was proposed to discriminate between the changes in afterload, preload and contractility. Results showed clearly discernible patterns of the respective load and contractility alternation.

Finally, the left ventricular continuous area was monitored continuously during the entire cardiac cycle as a measure of left ventricular volume dynamics in normal subjects and three patients with left ventricular abnormalities using echocardiographic automatic boundary detection. The left ventricular area thus obtained was plotted against its first derivative, to form a flow-volume estimates loop, in accordance with the flow-volume examinations used in respiratory physiology. Data obtained from the abnormal ventricles were presented as flow-volume estimates loops, exemplifying the possible use of the method.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 77 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2006:04
Keyword [en]
left ventricle, pressure and volume
National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:kth:diva-4211ISBN: 978-91-7178-507-7 (print)OAI: oai:DiVA.org:kth-4211DiVA: diva2:11259
Public defence
2006-12-15, 4X, plan 4, Nobels allé 8, Huddinge, 09:00
Opponent
Supervisors
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-09-22Bibliographically approved
List of papers
1. Correlation between a Mid-ventricular Volume Segment and Global Left Ventricular Volume Measured by the Conductance Catheter
Open this publication in new window or tab >>Correlation between a Mid-ventricular Volume Segment and Global Left Ventricular Volume Measured by the Conductance Catheter
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2001 (English)In: Scandinavian Cardiovascular Journal, ISSN 1401-7431, E-ISSN 1651-2006, Vol. 35, no 2, 129-135 p.Article in journal (Refereed) Published
Abstract [en]

Objectives-To investigate whether acute volume changes in single volume segments of the left ventricle can be correlated with global volume changes. If so, changes in global volume might be predicted from changes in segmental volumes.

Design-Volume changes were recorded in six pigs in five intraventricular segments, from apex to heart base, using the conductance catheter (at baseline, after 60 min of apical ischaemia, during preload reduction and afterload increase). A computer algorithm was created to calculate the instantaneous absolute difference between the curve shape of global and normalized segmental volume as a percentage of global stroke volume.

Results-For a mid-cardiac volume segment constituting 34 (14-39)% [median (range)] of global stroke volume, the mean difference over a cardiac cycle was 4 (1-8)% at baseline. Apical ischaemia resulted in apical dyskinesia, but did not influence the mid-cardiac segment.

Conclusions-The volume curve from a segment at mid-cardiac level seems to be a good estimator of the global volume curve, thus giving a foundation for estimation of global volume changes from such a segment.

Keyword
afterload, conductance catheter, ischaemia, left ventricular volume, preload, segmental volume
National Category
Biomedical Laboratory Science/Technology
Identifiers
urn:nbn:se:kth:diva-6516 (URN)10.1080/140174301750164853 (DOI)000168597100014 ()
Note
QC 20100906Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2017-12-14Bibliographically approved
2. Design of a single segment conductance catheter for measurement of left ventricular volume
Open this publication in new window or tab >>Design of a single segment conductance catheter for measurement of left ventricular volume
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2001 (English)In: Annual Reports of the Research Reactor Institute, Kyoto University, 2001, 151-154 p.Conference paper, Published paper (Refereed)
Abstract [en]

The objective of this paper is to investigate how to best position the sensing electrodes on a single segment conductance catheter, and to calculate the expected performance. Using electrode potential data, obtained with the present five segment conductance catheter in pig experiments, we have interpolated the electrical field at any given point of time, and calculated what volume curve to expect with only two sensing electrodes. Comparison shows that the deviation between our calculated method and the present one is stable and small. Mean deviation with optimized electrode positions was 0.05% per sample, and the maximum deviation found for a single time sample was 2.57%. This indicates that it is possible to build a thin single segment catheter with as good performance as for the present five segment conductance catheter.

Keyword
Left ventricular volume, conductance catheter, segment volume, pigs
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6517 (URN)10.1109/IEMBS.2001.1018873 (DOI)
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-09-22Bibliographically approved
3. Initial experience with a thin single segment pressure and conductance catheter for measurement of left ventricular volume
Open this publication in new window or tab >>Initial experience with a thin single segment pressure and conductance catheter for measurement of left ventricular volume
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2001 (English)In: Annual Reports of the Research Reactor Institute, Kyoto University, 2001, 103-106 p.Conference paper, Published paper (Refereed)
Abstract [en]

Aims: To evaluate a thin and soft multifunctionalcatheter for the simultaneous real time monitoring of leftventricular volume and pressure with special consideration toside elTects such as interference with normal cardiacelectrophysiology.Methods and results: In four pigs, pressure and volumewere simultaneously recorded by using the thin single segmentpressure and conductance catheter. Measurements were doneunder varied cardiac conditions: at baseline, during preloadreduction and afterload Increase. Volumes were calibrated withintracardiac ultrasound measurements. During preloadreduction the pressure and volume decreased as expected. Acautious afterload increase resulted in a corresponding pressureand volume increase, the maximum of the pressure curvechanged from early to late. Both SV and EDV increased. Thevery few arrhythmias were mainly caused by surgicalinterference.Conclusion: The present study demonstrates that our thinsingle segment conductance catheter for the simultaneousmeasurement of LV volume and pressure has a performancethat warrants further development with the goal to make themethod available for human use. In particular, the catheter didnot cause any arrhythmias.

Keyword
Left ventricular volume, Conductance catheter, segment volume
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6518 (URN)
Conference
23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society; Istanbul; 25 October 2001 through 28 October 2001
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-09-22Bibliographically approved
4. Conductance measurements in the left ventricle: a pressure-flow approach
Open this publication in new window or tab >>Conductance measurements in the left ventricle: a pressure-flow approach
2002 (English)In: IFMBE proc., 2002, 1012-3 p.Conference paper, Published paper (Refereed)
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6519 (URN)
Conference
2nd Eur. Medical and Biological Engineering Conf., EMBEC '02
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-09-22Bibliographically approved
5. Left ventricular pressure indicies help to evaluate loading conditions and contractility
Open this publication in new window or tab >>Left ventricular pressure indicies help to evaluate loading conditions and contractility
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2002 (English)In: IFMBE proc, ISSN 1680-0737, 1014-5 p.Article in journal (Refereed) Published
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6520 (URN)
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2012-02-10Bibliographically approved
6. Ultrasound tissue doppler measurements imply that conductance changes in the left ventricle during isovolumic phases are due to tissue motion.
Open this publication in new window or tab >>Ultrasound tissue doppler measurements imply that conductance changes in the left ventricle during isovolumic phases are due to tissue motion.
2002 (English)In: IFMBE proc.,, 2002, 1016-7 p.Conference paper, Published paper (Refereed)
Series
IFMBE proc.,, ISSN 1680-0737 ; Vol 3, 2002
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6521 (URN)
Conference
2nd Eur. Medical and Biological Engineering Conf., EMBEC '02,
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2010-09-22Bibliographically approved
7. The assessment of acute load and contractility changes by left ventricular pressure measurements
Open this publication in new window or tab >>The assessment of acute load and contractility changes by left ventricular pressure measurements
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2006 (English)In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 27, no 12, 1281-1292 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to establish whether analysis of the left ventricular pressure waveform provides indicative information about cardiac load and contractility and to develop an algorithm for computer-based assessment of changes in these variables. In eight healthy standard breed anaesthetized open-chest pigs, a high frequency response guide-wire mounted pressure sensor was introduced into the left ventricle. Preload reduction was induced by vena cava occlusion, afterload increase by an i.v. injection of phenylephrine and increased contractility by an i.v. injection of adrenalin. Left ventricular pressure waveform analysis was performed by plotting the slope of the pressure curve during the systolic ejection period versus maximal systolic pressure. The analysis revealed characteristic changes in left ventricular pressure and pressure waveform and identified easily discernible reaction patterns in the slope versus maximal pressure plot, specific for each provocation. Analysis of the left ventricular waveform provides indicative information about loading conditions and contractility. The proposed algorithm can easily be implemented in pressure monitoring systems allowing real-time assessment and discrimination of acute changes in preload, afterload and myocardial performance.

Keyword
monitoring, left ventricle, pressure waves, loading conditions, contractility
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6522 (URN)10.1088/0967-3334/27/12/003 (DOI)000242549900005 ()
Note
QC 20100922Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2017-12-14Bibliographically approved
8. Feasibility of creating estimates of left ventricular flow-volume dynamics using echocardiography
Open this publication in new window or tab >>Feasibility of creating estimates of left ventricular flow-volume dynamics using echocardiography
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2006 (English)In: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, no 4:40Article in journal (Refereed) Published
Abstract [en]

Background:This study explores the feasibility of non-invasive assessment of left ventricular volume and flow relationship throughout cardiac cycle employing echocardiographic methods.

Methods:Nine healthy individuals and 3 patients with severe left-sided valvular abnormalities were subject to resting echocardiography with automated endocardial border detection allowing real-time estimation of left ventricular volume throughout the cardiac cycle. Global and regional (6 different left ventricular segments) estimates of flow-volume loops were subsequently constructed by plotting acquired instantaneous left ventricular 2-D area data (left ventricular volume) vs. their first derivatives (flow).

Results:Flow-volume loop estimates were obtainable in 75% of all echocardiographic images and displayed in normal individuals some regional morphological variation with more pronounced isovolumic events in the paraseptal segments and significantly delayed maximal systolic flow paraapically. In patients with aortic stenosis, maximal systolic flow occurred at a lower estimated left ventricular systolic volume whereas in mitral stenosis, maximal diastolic flow was observed at a higher estimated left ventricular diastolic volume. Aortic regurgitation caused a complex alteration of the estimated flow-volume loop shape during diastole.

Conclusion:Non-invasive assessment of left ventricular flow-volume relationship with echocardiography is technically feasible and reveals the existence of regional variation in flow-volume loop morphology. Valvular abnormalities cause a clear and specific alteration of the estimates of the normal systolic or diastolic flow-volume pattern, likely reflecting the underlying pathophysiology.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-6523 (URN)10.1186/1476-7120-4-40 (DOI)2-s2.0-33750899084 (Scopus ID)
Note

QC 20100922

Available from: 2006-12-06 Created: 2006-12-06 Last updated: 2017-12-14Bibliographically approved

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  • nn-NO
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  • Other locale
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Output format
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